双節棍[nunchaku] nunchaku (two linked fighting sticks)
一双[issou] pair (esp. of folding screens)
一卵性双生児[ichiranseisouseiji] identical twins
双紙[soushi] written work (esp. a bound text, as opposed to a scroll)
自己双対[jikosoutsui] self dual

双刃[moroha] double-edged
双暗車[souansha] twin propellers
双殻類[soukakurui] bivalves
双眼[sougan] both eyes

インフラ開発[infurakaihatsu] infrastructure development
エンジン発動機[enjinhatsudouki] engine
バス発着場[basuhacchakujou] depot
発条[bane] spring (e.g. coil, leaf)
ロケット発射筒[rokettohasshatou] rocket launcher

異常発生[ijouhassei] plague
一触即発[isshokusokuhatsu] critical (touch and go) situation
一念発起[ichinenhokki] being resolved to (do something)
一発[ippatsu] one shot
一発かます[ippatsukamasu] to hit someone